Pulmonary embolism (PE) is a common disease with an incidence greater than 1 per 1000 and a three month mortality rate of 15%. Several treatments are available for PE, ranging from prophylactic anticoagulants to surgical embolectomy. Accurate patient treatment relies on proper risk stratification, which is done based on (i) clinical evaluation, (ii) determination of cardiac biomarkers levels such as troponin, and (iii) estimation of right ventricular size and/or function. PE increases the resistance of the pulmonary arteries. Depending on the extent of the disease and the general health of the patient, the right ventricle can compensate for such extra strain. Uncompensated pressure can result in right ventricular hypokinesis, which can lead to right ventricular enlargement among other issues.
Diagnosis of PE may be done with Computed Tomography Pulmonary Angiography (CTPA). Generally, the patient is injected with iodine contrast and imaged in a CT scan to evaluate opacifications in the pulmonary arteries. The cardiac chambers are included in standard CTPAs, therefore information on the state of the heart can be obtained without altering the current diagnostic protocol. The right ventricular to left ventricular diameter ratio (RV/LV), introduced more than 15 years ago, has been proven as a predictor of mortality in patients with severe PE.
Quantification of the RV/LV ratio can be done via several methods, such as volumetric measurements, diameter measurements in four chambers reformatting or in axial slices. Measuring on axial slices has been shown to be equivalent to measurements in 4 chamber views. Such measurements are often time consuming. To prevent increasing radiologist time, recent research has focused on qualitative evaluation of right ventricular enlargement as a biomarker for prognosis. However, such measurement is based on the experience of the reading radiologists.
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